Kestrel Ex

[AdrianParticipant]

Tony, is the nosecone deployment you’re describing for a single apogee deployment, or if it’s dual-deployment, how does that work?

Thanks.

-Adrian

[greywolves]

Thanks John, clear as mud, j/k. The reason i said snap ring, on my slimline tailcone, it use a snap ring for motor retetion, and its 38mm reduced from 54mm, thats on my Little Dawg DD. Also not MD rocket, makes since how you can have the tailcone on the Kestrel, very cool, part of the motor assembly.

So if thats the case, how do you guys keep the motor in the rocket? surely not friction fit on a L 😯

[John A. WilkeParticipant]

I’ve friction fit L’s (and K’s) probably 20 times. The longer motor lends itself well to friction fitting – more area for the tape to fit to.

FWIW, I’ve friction fit 75mm M’s several times as well. That is pretty much where you are at with min dia stuff. It works fine!

[Anonymous]

Adrian, This rocket will be dual deployment with all motors except for my longest 54mm Ex motor. When I fly it on the long motor it will be single deployment. I’m not sure if it will be with a reefed/line cutter or not. At this point I’m just planning on bringing it down as fast as I can. I fly out at Black Rock which makes it easier to do.

Greywolves. I friction fit all of my motors in min dia rockets. Here is a link to a 5″ P that was friction fitted.

http://www.youtube.com/watch?v=OZ2v48CoLqY&feature=related

Tony

[John A. WilkeParticipant]

Greywolves. I friction fit all of my motors in min dia rockets. Here is a link to a 5″ P that was friction fitted.

Bingo. You have relatively few options for motor retention in a min dia rocket. Tape is a good thing… I haven’t done a 5″ motor with friction fit, but I would if I was flying one in a 5″ rocket.

Nice boost, Tony.

What are you dreaming up for BALLS next year?

[AdrianParticipant]

Greywolves. I friction fit all of my motors in min dia rockets. Here is a link to a 5″ P that was friction fitted.

Bingo. You have relatively few options for motor retention in a min dia rocket. Tape is a good thing… I haven’t done a 5″ motor with friction fit, but I would if I was flying one in a 5″ rocket.

Two things can make friction fitting easier: Thrust rings and bulkheads.

If your motor doesn’t have a thrust ring (like some CTI loads designed to minimize drag), then you’ll want to have something up front for the motor to push against to take the motor thrust. If it’s a bulkhead, then it will withstand the deployment charge pressure too, and then all the friction fitting needs to do is keep the motor from falling out the back when the main comes out. But if there is nothing keeping the motor from moving forward other than the friction, the friction would need to withstand most of the motor thrust and all of the deployment charge pressure. Nobody does that for motors with thousands of lbs of thrust, do they?

[Warren B. MusselmanModerator]

I’m a firm believer in zipperless booster designs with a threaded rod going through the zipperless bulkhead to an eye-nut on MD projects. Problem comes when you’re talking about single-use motors.

[greywolves]

OK, next question, do they make a forward motor closure that fits CTI casings with an eye bolt? certain sizes? 38mm, 54mm…..250mm 😯

Warren, how would the rod be attached to the motor case?

Adrian, yeah no thrust, if anyone could figure out a way to avoid that, it would be you. Poor piece of tape rolled up into a little miniature cigarette, as the motor shot threw my nosecone, hehe.

[Warren B. MusselmanModerator]

Threaded forward closure in all cases. Alternative for motor cases without a threaded hole would be a bulkhead on a T-nut plus tape to prevent rear-ward loss of the motor case.

CTI doesn’t have that on 38mm cases, but those I wouldn’t think twice about friction fitting with masking tape

Warren

[Anonymous]

I was able to get some work done on my KestreL last week. One thing I wanted to say was that, there is nothing wrong with the stock KestreL. I’m doing some stream lining, which the average person can do to squeak out a few more feet.
After playing with the fins in Rocsim. I went with cutting .375 off the root edge of the fins. This reduced the fin span to 2.375. I roughed up the fins and body tube with 60 gritt and tacked the fins in place. The fin jig made this very easy to do. The slotted body tube will add lots of strength to the fins and is a great idea for min dia rockets.

I also got most of the electronics bay done. I cut the coupler/electronics bay down to 4.25″ long. For the board I used some .063 G-10 and sandwiched some balsa wood between them leaving space for the threaded rod to pass through. I was able to get an ARTS 2, 9 volt battery and a Bee Line TX in there. For a switch I’m just going with twisted wires,

In the next couple of days I hope to get to glassing the fins on.

Tony

[Author]

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